Effects of calcium channel blockers on cold-induced vasodilatation and elevated sympathetic tone in the canine internal maxillary artery bed.

This study was concerned with the interactive effects of cold-induced vasodilatation, blockade of voltage-sensitive Ca2+ channels and sympathetic nerve stimulation in the nasal vascular bed of anesthetized dogs. To estimate the distribution of the internal maxillary artery blood flow to capillaries and to arteriovenous anastomoses (AVA), the microsphere technique in combination with electromagnetic flowmetry was used. Intraarterial infusion of verapamil resulted in a dose-dependent vasodilatation and a redistribution of the internal maxillary artery blood flow. Simultaneously applied electrical stimulation of the cervical sympathetic trunk resulted in a significant fall in blood flow, caused mainly by a decrease in capillary flow. Verapamil infusion combined with cold exposure led to a simultaneous elevation of the AVA and capillary flows. When electrical stimulation of the cervical sympathetic trunk was also applied, the AVA and capillary flows were affected in different manners, depending on the sequence of the stimulations. Analysis of capillary flow data in the various nasal and facial tissue compartments indicates that cold exposure, blockade of the voltage-dependent Ca2+ channels and an elevated sympathetic tone modify the local nutritive blood flow.